The few things I could understand about that.

• Modern fighter jet have a huge software part. Remember the Top-Gun film where the F-14 needed an officer on the backseat to monitor radar, position, identify target and tons of stuff I have no idea about ? In machine like the F-35 it’s replaced by a computer. Like any other software it’s relatively easy to implement some permission to use-it.

• Modern fighter are pretty complex piece of hardware, and you can’t just have a good mechanic reproducing a part with their own tools and need a whole supply chain running

• It’s not even that new nor American only. Remember the Falkland war ? Airbus sent some french engineer to help Argentinian operating the Exocet missile because sinking a British warship is good for marketing and once done, the French gov told their British allies where the missile batteries were located (because their allies after all). Except that with modern technology, you can do both without having to have a defence industry engineer travelling. And realistically, any country exporting weapon would have way to make sure the weapon won’t be used against them (while not limiting too much their usage to not fuck their marketing)